JAVA WEB 用户点击按钮，根据URL下载在线文件到客户端 下载文件 下载图片

    
    @RequestMapping("/download")
    @ResponseBody
    public void downloadImg(String imgUrl,String hospitalName, HttpServletResponse response){

        try {
            // 构造URL
            URL url = new URL(imgUrl);
            // 打开连接
            URLConnection con = url.openConnection();
            // 设置请求超时为5s
            con.setConnectTimeout(5 * 1000);
            // 输入流
            InputStream is = con.getInputStream();
            // 1K的数据缓冲
            byte[] bs = new byte[1024];
            // 读取到的数据长度
            int len;
            // 输出数据流
            ByteArrayOutputStream output = new ByteArrayOutputStream();
            // 开始读取
            while ((len = is.read(bs)) != -1) {
                output.write(bs, 0, len);
            }

            response.reset();
            response.setHeader("Content-Disposition", "attachment; filename="+
                    new String(hospitalName.trim().getBytes("utf-8"),
                    "iso8859-1"));
            response.addHeader("Content-Length", "" + output.toByteArray().length);
            response.setContentType("application/octet-stream; charset=UTF-8");
            IOUtils.write(output.toByteArray(), response.getOutputStream());

            output.close();
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }